1. Field of the Invention
The present invention relates to a film formation apparatus for a semiconductor process for forming a thin film on a target object, such as a semiconductor wafer, inside a vacuum container by use of at least two reactive gases of different types. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target object, such as a semiconductor wafer or a glass substrate used for an FPD (Flat Panel Display), e.g., an LCD (Liquid Crystal Display), by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target object.
2. Description of the Related Art
Owing to the demands of increased miniaturization of patterns used in semiconductor devices, it has become more important to form embedded structures of high quality inside depressed portions in the patterns. For example, in order to provide device isolation areas on a semiconductor wafer, various techniques have been proposed concerning an STI (shallow trench isolation) structure, which includes a trench formed in the wafer and an insulating film embedded in the trench. As regards techniques of this kind, it has become more difficult to provide films good in filling performance as well as film quality, along with the increased miniaturization of patterns. In the present circumstance, oxide films formed by a combination of a PSZ (polysilazane) film coating method and an HDP (high density plasma) method are widely used as embedded films of this kind. However, where a CVD (chemical vapor deposition) method, such as the HDP method, is used, voids are easily generated at overlap portions of films deposited on the sidewall of a trench. Consequently, problems arise such that deterioration in film quality, such as an increase in etching rate, is caused, and deposition in deep trenches is difficult. Further, along with the increased miniaturization of patterns, fluctuation of the shape of resist masks influences more on the shape of depressed portions, and may cause depressed portions to have a reversely taper shape that is wider toward the bottom. Where a depressed portion has a high aspect ratio and a reversely taper shape together, it is particularly difficult to embed a film therein.
U.S. Pat. No. 7,153,542 discloses an apparatus configured to rotate a table with a wafer placed thereon relative to a gas supply section, while sequentially supplying different reactive gases onto the wafer, to perform film formation cycles including a plasma process and a thermal process. Jpn. Pat. Appln. KOKAI Publication No. 8-162449 discloses a film formation method utilizing liquid phase epitaxy for improving characteristics for embedding a film, along with repetition of plasma irradiation and thermal annealing for improving the film quality. Jpn. Pat. Appln. KOKAI Publication No. 2004-47644 discloses a technique for forming an oxide film by liquefying TEOS gas on the substrate and then supplying oxygen gas under heating.